Variable-focal-length lens

Abstract

Disclosed is a variable-focal-length lens whose focal length can be electrically controlled by applying an electric field of uniform intensity distribution to a compound lens including at least one lens formed of electrooptic crystal and varying the intensity of the applied electric field.

What I claim is: 
     
       1. A variable-focal-length lens comprising: a lens system including at least one set of electrooptic crystals cemented together on curved surfaces thereof so that the directions of their respective axes of rotatory inversion are coincident with each other and so that the directions of their respective two corresponding rotation axes differ from each other;   means for applying an electric field of uniform intensity distribution to said cemented surfaces of said electrooptic crystals so as to make said cemented surfaces refraction surfaces having a lens action; and   means for varying the intensity of the electric field to be applied, to thereby vary the focal length of said lens system.   
     
     
       2. A variable-focal-length lens according to claim 1, wherein a polarizing plate is disposed on the light path of a light beam passing through said compound lens. 
     
     
       3. A variable-focal-length lens according to claim 1, wherein said means for applying an electric field comprises parallel flat electrodes attached to said electrooptic crystals. 
     
     
       4. A variable-focal-length lens according to claim 1, further comprising means provided on the light path of a light beam passing through said compound lens for varying the polarization direction of said light beam. 
     
     
       5. A variable-focal-length lens according to claim 3, wherein the intensity of the electric field to be applied is varied by controlling the voltage of a variable power source connected to said parallel flat electrodes. 
     
     
       6. A variable-focal-length lens according to claim 4, wherein said means for varying the polarization direction of said light beam comprises a polarizing plate and means for rotating said polarizing plate about the optical axis.